The Iraqi government declared a state of emergency and imposed a curfew Friday after gunmen set up roadblocks in central Baghdad and opened fire on U.S. and Iraqi troops outside the Green Zone. Iraqi Prime Minister Nouri al-Maliki ordered everyone off the streets of the capital from 2 p.m. until 5 p.m.

According to the AP, American and Iraqi forces also clashed with gunmen in the Dora neighborhood in south Baghdad.

Two U.S. troops died when a roadside bomb struck their vehicle southeast of the capital, the U.S. military said Friday. The US military also said two U.S. Marines died in combat in Anbar province during separate attacks on Wednesday and Thursday, and a soldier died elsewhere in a non-combat incident on Wednesday.

Meanwhile, a car bomb ripped through a market and nearby gas station in the southern city of Basra, killing at least five people and injuring 18, including two policemen, police said. A bomb also struck a Sunni mosque in Hibhib, northeast of Baghdad, killing 12 worshippers and wounding 15 in the town where Abu Musab al-Zarqawi was slain this month, police said.

At least 19 other deaths were reported in Baghdad.

Throughout the morning, Iraqi and U.S. military forces clashed with attackers armed with rocket-propelled grenades, hand grenades and rifles in Haifa Street, which runs into the Green Zone.

Four Iraqi soldiers and three policemen were injured in the clash, police Lt. Maitham Abdul Razzaq said.

Gunmen also attacked a group of worshippers marching from Sadr City, the Shiite slum in eastern Baghdad, to the Buratha mosque on the other side of the city to protest a suicide attack a week ago on the Shiite shrine. At least one marcher was killed and four were wounded, Lt. Ahmed Mohammed Ali said.

Police said they found the bodies of five men who apparently were victims of a mass kidnapping from a factory on Wednesday. The bodies, which showed signs of torture and had their hands and legs bound, were floating in a canal in northern Baghdad, police Lt. Maitham Abdul-Razzaq said.

In another development, the U.S. military said it killed four foreign "insurgents" in a raid north of Fallujah. Separately, the US military said, it detained a senior leader of al-Qaeda in Iraq during a raid northeast of Baghdad.